Presentation libraryNew symbols introduced in S-52 PresLib 4.0.0
The file name uses the IHO Producer Code (AA), followed by the navigational purpose and the individual cell code given above. Revision will be by new edition, and so the update number is always ".000". An example of a full file name is: "AA5C1AB1.000" Spatially, the "harbour" scale Chart 1 detail cells ("N"=5) are laid out in a 3 x 3 matrix with the Colour Test display cell below (to the south), and all are covered by the index cell on the "approach" scale ("N"=4). They are located in the West African desert at 15 degrees north, 5 degrees west, where there shall be no danger of their being called up as real chart cells (unless river traffic on the R. Niger above Timbuktu increases drastically.) The EN Application Profiles of S-57 Appendix B1 are used, with arbitrary values entered for certain items (such as vertical datum) which do not apply to Chart 1. (This is done to minimise the changes to ECDIS software needed in order to process these special purpose Chart 1 files in an ECDIS.) The IHO agency code (1810) is used in the AGEN sub-field of the DSID field, and the PRSP field is given the value {3} to distinguish it from the values used for the ENC Product Specification. 18.2.5 RevisionsRevisions will be made by whole file replacement, i.e. by issuing a new edition, as indicated in the EDTN sub-field of the DSID field. 18.2.6 PackagingThe pseudo S-57 data files are part of the Digital Presentation Library. 18.2.7 PresentationThe Chart 1 files are symbolized by the NEWOBJ look up table entries triggered by the SYMINS attribute of the generic object NEWOBJ introduced by the supplement No. 1 of S-57 Edition 3.1.1. The README files give some specific Mariner settings, such as safety contour, that are required to give the correct display. The ECDIS Chart 1 and Colour Test diagram cells shall be displayed full-screen (270 x 270 mm), i.e. at or larger than the compilation scale. Otherwise features such as centred symbols may not be correctly illustrated. The Mariner shall be able to cursor-pick on any symbol on the Chart 1 display and get a text read-out of the symbol meaning (LXPO field of the symbol library). 18.3 Displaying the Colour Test Diagram18.3.1 Introduction; providing the diagramThe colour generating capability of any type of display screen will deteriorate with age and the Colour Differentiation Test diagram is provided to enable the Mariner to verify that his display screen still retains the colour differentiation capability needed to distinguish between the various colour-coded areas, lines and point symbols of the ECDIS display. The diagram will not be true to colour unless it is projected on a calibrated monitor and is generated using the colour tables of Appendix A. Two methods of providing the diagram are: a) Use the S‑57 format file labelled “C1WOO” containing the Colour Differentiation Test Diagram, which is included on the Presentation Library distribution CD. This file shall be drawn so that the extent of the imaginary chart data covers the entire ECDIS display. Because the file uses pseudo-S-57 cartographic objects it shall be displayed using the special look-up provided for the digital ECDIS Chart 1. b) Use the graphics file illustrated in section 16.3 as a model. Based on this model, reproduce the same pattern of rectangles and lines on the screen, but present them in the correct colours using the colour tokens given immediately below and the colour tables of Appendix A. The diagram consists of twenty numbered squares extending over the whole of a 270 x 270 mm screen. Each square is coloured with one of the four main background area shades (such as shallow water blue, DEPVS), and each carries a two-pixel wide diagonal line in one of the important line or symbol foreground colours (such as planned route red, PLRTE). These are arranged as follows: Four main background colours:
Six important foreground colours:
Note: Remember that a tif, .pdf or other source will not be true to colour unless it has been specifically modified to access the colour tokens and colour tables used by the ECDIS. Although originally designed for use on CRTs, this test shall be extended to LCD and other screens. 18.3.2 Using the diagramThe Colour Test shall be applied on the day and dusk colour tables. Before the Colour Test diagram is used, the black-adjust symbol SY(BLKADJ) shall be brought up on the screen and the contrast and brightness controls (or equivalent controls for an LCD) shall be adjusted as follows: First, set contrast to a maximum, brightness to a minimum. Look at the black-adjust symbol. Then either: 2A. If the centre square is not visible, turn up the brightness until it just appears. OR: 2B. If the centre square is clearly visible (with contrast at maximum, brightness at minimum), turn the contrast down until the inner square disappears, then turn contrast back up until the inner square is just visible again. (If the above adjustment is not successful, select a more appropriate colour table and repeat this procedure). The "black level" is then correctly set. If a brighter display is required use the contrast control, but preferably do not adjust the controls unless lighting conditions on the bridge change. The test consists of being able to distinguish the background colours and to pick out the like foreground colours, i.e. to say that squares 3, 5, 11, 15, 18 and 20 all have a shallow water blue background, and that squares 3, 10 and 17 have a grey line. NOTE: The test above uses the black-adjust symbol for the purpose of a type approval test. The other purpose of the black-adjust symbol SY(BLKADJ) is to allow the mariner to adjust the display for ambient illumination on the bridge of a ship. An ECDIS shall have the black-adjust symbol displayed whenever the mariner is adjusting the display (i.e. depending on the technology of the display brilliance, brightness, contrast, etc.), as required by section 4.2.4.5 of S-52 e6.1.0. 18.4 Grey ScaleA grey scale may be used by service technicians to detect display ageing or other display performance issues. Eight grey strips are recommended, spaced between the minimum and the maximum luminance for each of the five mandatory colour tables. The bit levels or signal levels producing the grey levels are evenly spaced from the level producing white to the level producing black. In order to select the appropriate grey level from a large set of available grey levels, use one of the following models: Bit Levels in Software: Given n levels of grey that can be displayed on a screen, with 0 for black and w = n - 1 for white. We want to select a subset of m levels that are as evenly spaced as possible. The interval between the n levels to create m levels is ΔV = w/(m-1), which may not be an integer. So, the levels to select are the (integer) values of Vi= int[(i-1) ΔV] for i = 1, 2, ..., m, or Vi= 0, int(ΔV), int(2ΔV), int(3ΔV), ..., int[(m-1) ΔV], with int[(m-1) ΔV] = w for white. For example, if there are n = 256 = 28 levels from which we select m = 8 levels, white is w = 255; the interval is ΔV = 36.4286, and the chosen levels are: 0, 36, 73,109, 146, 182, 219, 255. Analog Signal Levels: For analog signals, if Vw is the white level and Vb is the black level, then for m levels the signal step size is ΔV = (Vw - Vb)/m and Vj= Vb + jΔV. Supply and Amendment of the Digital Presentation LibraryThe word-processed version of the Presentation Library is the "official" version. A limited digital version in .dai format is provided on the CD-ROM containing the word-processed Presentation Library as a manufacturer's option for edition 4.0.0, but may not be provided for succeeding editions. This digital version consists of look-up tables; symbols; and colour tables and is supplied in ASCII format in the .dai file. The edition number appears in the LBID line at the start of the .dai file where it is coded digitally and also spelled out in plain language. 19.1 Amending the digital Presentation Library(See also S-52, sections 1.2.3 and 1.2.4) Amendments to the Presentation Library, if available, will be posted on the IHO website (www.iho.int > Standards & Publications > Download > Maintenance Section). An immediate amendment (but not a deferred amendment) will change the edition number of the Presentation Library. The edition number of the PresLib installed shall be available to the Mariner on request. 19.2 Internal Structure of the Transfer FileThe PSLBmm_n.dai file has a particular internal structure. In the format description (see section 12), several constructs (modules, fields, etc.) are used to convey colour tables, look-up tables, symbols, patterns and linestyles. The transfer file is formed of one or more modules. Each module is formed of one module record. Each module record is formed of one or more fields which in turn is formed of one or more subfields. This structure is explained below: PSLBmm_n.dai (module group) │ │ └──── modules [N] │ │ │ └────── module record [1] │ │ │ └───── fields [N] │ │
The lowest level construct, the subfield, shall only contain one elementary data item, for example, one colour coordinate or one symbology instruction. Formatted subfields, such as the subfields that contain the vector image definitions, shall be further resolved by an application program. In this specification, subfields are not divisible. The field tag is a unique 4 character field type which links an instance of a field type in a data record to the data descriptive record that defines the syntax of that field type. The subfield label is a 4 character label, present only in the data descriptive record of a file, required to identify the subfields within a field type. A label preceded by an "*" signifies that that subfield, and any subsequent ones, repeat within the field. This, therefore, indicates the presence of an array or table, for which the subfield labels provide the column headings. Subfield data type codes uses data types as follows: A signifies character data, I signifies implicit point representation (integer), R signifies explicit point representation (real or float), An extent of X(n) indicates a fixed length subfield of length n. An extent of X(1/15) indicates a variable length subfield terminated by the delimiter "1/15" (that is ASCII 1F hexa-decimal or 31 decimal). __________ PresLib Edition 4.0.0 Part I September 2014 Download 7.92 Mb. Share with your friends: |